List Set Map 数组 转换
1.list转set
Java代码 复制代码

1. Set set = new HashSet( new ArrayList());

Java代码 复制代码

1. Set set = new HashSet( new ArrayList());

Set set = new HashSet(new ArrayList());


2.set转list
Java代码 复制代码

1. List list = new ArrayList( new HashSet());

Java代码 复制代码

1. List list = new ArrayList( new HashSet());

List list = new ArrayList(new HashSet());


3.数组转为list
Java代码 复制代码

1. List stooges = Arrays.asList( "Larry" , "Moe" , "Curly" );

Java代码 复制代码

1. List stooges = Arrays.asList( "Larry" , "Moe" , "Curly" );

List stooges = Arrays.asList("Larry", "Moe", "Curly");


此时stooges中有有三个元素。
4.数组转为set
int[] a = { 1, 2, 3 };
Java代码 复制代码

1. Set set = new HashSet(Arrays.asList(a));

Java代码 复制代码

1. Set set = new HashSet(Arrays.asList(a));

Set set = new HashSet(Arrays.asList(a));


5.map的相关操作。
Java代码 复制代码

1. Map map = new HashMap();
2. map.put( "1" , "a" );
3. map.put( '2' , 'b' );
4. map.put( '3' , 'c' );
5. System.out.println(map);
6. // 输出所有的值
7. System.out.println(map.keySet());
8. // 输出所有的键
9. System.out.println(map.values());
10. // 将map的值转化为List
11. List list = new ArrayList(map.values());
12. System.out.println(list);
13. // 将map的值转化为Set
14. Set set = new HashSet(map.values());
15. System.out.println(set);

Java代码 复制代码

1. Map map = new HashMap();
2. map.put( "1" , "a" );
3. map.put( '2' , 'b' );
4. map.put( '3' , 'c' );
5. System.out.println(map);
6. // 输出所有的值
7. System.out.println(map.keySet());
8. // 输出所有的键
9. System.out.println(map.values());
10. // 将map的值转化为List
11. List list = new ArrayList(map.values());
12. System.out.println(list);
13. // 将map的值转化为Set
14. Set set = new HashSet(map.values());
15. System.out.println(set);

Map map = new HashMap();
map.put("1", "a");
map.put('2', 'b');
map.put('3', 'c');
System.out.println(map);
// 输出所有的值
System.out.println(map.keySet());
// 输出所有的键
System.out.println(map.values());
// 将map的值转化为List
List list = new ArrayList(map.values());
System.out.println(list);
// 将map的值转化为Set
Set set = new HashSet(map.values());
System.out.println(set);


6.list转数组
Java代码 复制代码

1. List list = Arrays.asList( "a" , "b" );
2. System.out.println(list);
3.
4. String[] arr = (String[])list.toArray( new String[list.size()]);
5. System.out.println(Arrays.toString(arr));

Java代码 复制代码

1. List list = Arrays.asList( "a" , "b" );
2. System.out.println(list);
3.
4. String[] arr = (String[])list.toArray( new String[list.size()]);
5. System.out.println(Arrays.toString(arr));